Checking Vacuum System

HINT: Any diagnostic trouble codes stored in the engine control module (ECM) or forward sensing module (FSM) should be remedied first. 

• Ignition on.
• Depress the brake pedal several times and check that it feels hard and responsive.
• Keep the brake pedal depressed and start the engine.

  The brake pedal should travel and feel softer.

Was the function OK? 

• YES 

  Refer to CHECKING BRAKE PRESSURE SENSOR 

• NO 

  Refer to CHECKING VACUUM SYSTEM 

Does the vehicle have a vacuum pump? 

• YES 

  Refer to CHECKING THE VACUUM PUMP 

• NO 

  Refer to CHECKING VACUUM SYSTEM 

Check the vacuum and power brake booster's condition.

Were the hoses and the power brake booster OK? 

• YES 

  Refer to VERIFICATION 

• NO 

  Refer to CHECKING BRAKE PRESSURE SENSOR